1. Field of the Invention
The present invention relates to image stabilization of image capture data.
2. Description of the Related Art
A digital image easily allows enlarged-scale display of over 100% of its original size using a personal computer. In an enlarged image, image blur caused by even a slight camera shake stands out. For this reason, as image capturing devices of digital cameras gain higher resolutions, a process for correcting camera shake at image capture time has received a good deal of attention.
Image stabilization methods include those implemented directly in hardware and those implemented in software. In methods implemented in hardware, a gyro sensor is mounted on a camera, and the influence of camera shake is eliminated by driving a lens and using an image capturing device to cancel vibrations of the camera during exposure based on an output signal from the gyro sensor. An image stabilization method by means of a lens optical system is described in, for example, Japanese Patent Laid-Open No. 2002-214657 (reference 1).
The hardware image stabilization method poses problems related to an increase in the number of components as well as an increase in manufacturing cost. Implementation of a similar function in inexpensive digital cameras demands a software image stabilization method.
As the software image stabilization method, a method of preparing a plurality of images obtained by short exposure (to be referred to as short exposure images hereinafter), and synthesizing these images is available (for example, Japanese Patent Laid-Open No. 2007-243774 (reference 2)). The invention of reference 2 implements image stabilization by correcting the respective deviations of a plurality of images, which are continuously captured each for a short exposure time that permits camera shake, and synthesizing the plurality of deviation-corrected images.
Also, a technique which corrects camera shake by coding a shutter opening and closing pattern, and using the coded opening and closing pattern has been developed. For example, an invention described in Coded Exposure Photography: Motion Deblurring using Fluttered Shutter, ACM SIGGRAPH 2006 (reference 3) is one of such techniques. The invention of reference 3 captures images for randomly coded exposure times, and corrects camera shake using an inverse matrix of the exposure time codes.
Reference 3 corrects image blur due to, for example, camera shake using a technique called coded exposure. Coded exposure is a technique that corrects image blur using a correlation between images obtained by irregularly opening and closing a shutter during a designated exposure time (to be referred to as a fluttered shutter hereinafter), and the shutter opening and closing pattern.
However, an exposure amount (an integral value of exposure amounts during an exposure period) obtained by the fluttered shutter is lower than that obtained when a shutter is open for a proper exposure time, and a captured image becomes dark. Although the brightness of a captured image can be increased by gain adjustment, image quality often degrades due to an increase in noise.